Elements of a computer system may need to exchange information. For example, a Central Processing Unit (CPU) of a computer system may need to store information into and/or retrieve information from a memory unit. In some cases, Input Output (IO) information may be exchanged over one or more interfaces within the computer system. Moreover, the computer system may need to maintain the consistency of information that exists within various elements. For example, data stored in the cache of one element might need to match data stored within another element. Methods and apparatus that permit the flexible and efficient transfer of information within a computer system, while maintaining such consistency, may therefore be desirable.